2015 Infiniti Q50: check engine light

Filed May 14, 2026 · Electrical, Engine · MD

The valve body on these cars are useless. Driving down a highway and cant shift out of 3rd gear almost had a car re-end me. Today I am driving and the ECU is not responding I see the check engine light on then I'm like not again. This would be the 3rd valve body I replaced. First I replaced the whole transmission thinking that is what I needed and advised that the valve body and the transmission are one. Yet no they come in parts. Anyways today I am waiting to get home, but the car is not reading my key fob why? Then the ECU and code U0100 is popping up. Something new and turns the car off. The shifting that happen earlier was just a light bulb of I already knew what is wrong. I felt the car shift with a hunch so I looked at my dash board and saw the check engine light again and was like not again. Please not again. Now on the dash board I see AWD and chassis issue. Then online I am told electrical problem and or ECU module not reading correctly. Like what is up with these push to starts. They are becoming a headache. I need to know just why I am replacing my valve body now for the 4th time???? This all can cause an accident that my car randomly slows down.

Filed Mar 5, 2026 · Transmission · 99,000 miles · FL

The contact owns a 2015 Infiniti Q50. While driving at various speeds, the transmission was slow to shift. The vehicle failed to properly accelerate while depressing the accelerator pedal, and the check engine warning light remained illuminated. The vehicle was taken to a local transmission mechanic to be diagnosed, and it was determined that the gear ratio and speed sensor inside the transmission valve body were faulty, and that the valve body needed to be replaced. The valve body was replaced, and the failure was repaired; however, one week later, the failure reoccurred. The vehicle was taken back to the mechanic, and it was informed that the transmission needed to be replaced. The vehicle was not yet repaired. The manufacturer and local dealer were not contacted. The failure mileage was 99,000.

Filed Aug 26, 2025 · Acceleration, Electrical · CA

The car just slowed down super fast on freeway almost got rear ended. It would not go past 3rd gear. Poor acceleration. Could have caused a huge accident. I got it diagnosed and they said it is valve body/speed sensor/tcm and they said this is a COMMON problem for 2015 Q50. I replaced this part 2 years ago and here we go again. Shop diagnosed and said this tcm (transmission control module which is in the transmission) but they have to change whole transmission. Everything happened all the sudden then check engine light came on.

Filed Jul 9, 2025 · Engine, Transmission · 94,150 miles · CA

The contact owns a 2015 Infiniti Q50. The contact stated while driving 40 MPH, the accelerator was depressed; however, the vehicle failed to shift into gear properly, with the check engine warning light illuminated. The vehicle was able to be restarted. The vehicle was taken to an independent mechanic, where it was diagnosed that the transmission valve body had failed, and the transmission needed to be replaced. The vehicle was not repaired. The dealer was not contacted. The vehicle was not diagnosed or repaired. The manufacturer was made aware of the failure. The approximate failure mileage was 94,150.

Filed Jun 4, 2025 · Acceleration, Transmission · TX

Just over 1 week ago, I was leaving a parking lot and driving back to my home when my car wouldn't accelerate past about ~10-15 miles per hour and wasn't shifting gears. When I took my foot off the gas pedal, the gear just dropped immediately from above third to first gear and the car shook. I first noticed this when already out of the parking lot and pulling off from a median onto the road, with no engine light or other warnings. I quickly pulled into the turn lane where there wasn't traffic and turned the car off and back on. It was the same but luckily I was in eyes view of my apartment, so I drove under 10 mph and made it home. I took the vehicle to a transmission service center and the error code that came up on the computer was (P0500 - Vehicle Speed Sensor A), which the service center said is an issue with the "valve body" inside the transmission, specifically the "TCM - Transmission Control Module" that sits on top of the valve body. I contacted multiple Infiniti service centers and they all confirmed that the valve body for my vehicle (part# 31705-x133a) is back ordered by over a month and could be longer until they have it. They do not sell the Transmission Control Module separately. The valve body was quoted to me for $2200 for the part alone. I attempted to install an aftermarket valve body and a new error code came up on the computer (PO720 - Output Speed Sensor Circuit). I kept the original valve body and will hold onto it. Doing some more research, this appears to be a common issue with the Infiniti Q50 - [XXX] In addition to the reddit thread above, a quick google search for Infiniti Error codes P0500 and PO720 point to multiple sources indicating the same common experience and outcome. My vehicle has 110k miles and users in the reddit comments are also reporting the same issue with the TCM Transmission Control Module occurring between 85k - 100k miles in all cases. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Oct 23, 2024 · Airbags · NC

Upon driving when purchased the Engine Light for the Air Bags illuminated. Upon researching the issue the problem seems to be a common problem for vehicles of this make and problem. 90% of the time requiring the owner to take the vehicle to the dealership.Since it is a trend and ongoing I wanted to report the issue.

Filed Aug 6, 2024 · Transmission · NY

Transmission valve body failed and is a common problem for 2014-2016 I was on a busy road and the car threw check engine light and wouldn’t accelerate any more. I risked my safety and others because I was stopped in the middle of the road and lots of commuters passing by and the vehicle was fully registered and inspected by the state prior that happened but it’s a common problem that you’ll never know when it will fail.

Filed Apr 14, 2024 · Transmission · AL

My engine light came on at 115,946 miles causing my vehicle not to accelerate or shift properly which could have resulted in a accident. The vehicle was diagnosed at local Nissan dealership with code P0720 and P0500 stating vehicle need a transmission. Prior to this diagnose this vehicle was diagnose twice by a Nissan and Infiniti dealership concerning the shifting and acceleration issues but could not duplicate the issue at the time. I see where numerous car buyers are stating they’re having the same issues with the Infiniti brand at low miles and high miles.

Filed Oct 4, 2023 · Acceleration, Electrical · GA

My car would not accelerate over 40 mph randomly after work. Once i noticed and tried to shift to a lower gear the car did not shift gears at all. When these things first happened there was no indicator lights on. The next morning the check engine light came on and the code pulled was P0720. After finding a repair shop to look further into the issue I was advised the car needed a new transmission to fix the issue. $4,000+ for the repair and as i google the issue I see that this is a common issue and it seems to always happen unexpectedly side note: also should be a recall on driver side blend door.. i almost died this summer due to cold air only blowing on one side in the middle of summer in 100• degree weather.

Filed May 30, 2023 · Acceleration, Electrical · 56,000 miles · AL

The contact owns a 2015 Infiniti Q50. The contact stated that while driving at highway speeds, the vehicle inadvertently slowed down. The vehicle failed to accelerate. The check engine warning light was illuminated. The vehicle was towed to the local dealer where it was diagnosed that a valve body replacement was needed. The vehicle was not repaired. The manufacturer was contacted, and the contact was informed that the vehicle was not covered under warranty. The failure mileage was approximately 56,000.

Filed May 16, 2023 · Acceleration, Transmission · TX

The speed sensor on car seems to have failed unexpectedly while driving over a bridge. The car would barely move and could have become a dangerous situation for multiple people had it been typical traffic. The issue seems to be that although the sensors are corrupted, the entire valve body or transmission must be replaced to solve the issue leaving the car inoperable. The car is currently at a repair shop. The engine light did come on shortly after. PLEASE ISSUE RECALL.

Filed Mar 31, 2023 · Transmission · FL

I was driving perfectly fine and i stopped at a red-light. I went to accelerate and the car wouldn't shift out of first gear and then check engine light came on. I pulled over and scanned the codes, it showed code p0500. After bringing to shop and reading thousands of different things from people who own the car online all said the same thing. Transmission valve body is shot. I almost got rear ended when i let off the gas because the engines rpms were so high casuing quick engine braking.